1. Field of the Invention
The invention relates to an electrochemical cell, in particular a secondary cell, with systems for circulating electrolyte liquid, electrolyte suspension or the like, for example a zinc-bromine battery, and to a process for the manufacture thereof.
2. Description of the Prior Art
Electrochemical cells with circulating electrolyte liquid, such as zinc-bromine batteries which are generally representative of such cells, are illustrated in U.S. Pat. Nos. 4,105,829; 4,124,478; 4,277,317; 4,279,752, 4,285,794; 4,286,027; 4,312,735; 4,346,150; 4,377,445; 4,379,814; 4,396,689 and 4,400,448. It is desirable to design the electrochemical cell in such a way that the smallest possible spatial volume is required, with the catholyte and the anolyte being stored in their own reservoirs and being pumped through the battery's electrolyte systems by appropriate pumps, as for example by means of pumps having a common drive motor. Plastic materials have proved particularly suitable for both the separators and the electrodes, with the electrodes having portions containing, for example, plastic-bonded carbon, carbon filled plastic, graphite, carbon black activated carbon or the like. Electrodes of this kind are generally for the bipolar type of batteries.
A battery of this type is disclosed which has plastic separators and carbon-filled electrodes. In the separators, depressions are employed, which provide distribution channels for the electrolyte into and out of the electrode anode or cathode spaces. The electrodes and the separators are constructed of polypropylene, polyethylene or copolymers thereof and are operatively joined together generally either by means of a suitable adhesive material, plastic welding, heat sealing or thermal welding. The application of adhesive material is, however, extremely difficult to control in practice. An unduly small or an unduly large application of adhesive material must be avoided, since otherwise a sufficiently tight liquid connection is not formed or the distribution channels are blocked by any excess adhesive material, which can cause inadequate electrolyte flow to or from a cell. Thermal welding of the plastic components has proven to be a preferable method for joinder of electrodes and separators into cell elements or assemblages.